Chemical reduction plating process and bath



Unite States Patent corporation of Delaware No Drawing. Filed Oct. 1,1958, Ser. No. 764,490 20 Claims. (Cl. 106-1) This invention relates tochemical plating and more particularly it relates to novel chemicalplating processes wherein nickel-boron and cobalt-boron alloys areplated from new aqueous chemical plating baths.

This application is a continuation-in-part of application Ser. No.694,097, filed Nov. 4, 1957, and now abandoned.

Plates of the aforementioned alloys have particularly desirableproperties as metal plates or coatings and are bright, hard and uniformin thickness. They also have excellent wear and corrosion resistance.

These plates may be formed through the use of a borohydride as areducing agent as disclosed in my copending applications filed of evendate herewith and identified as P.C. 2839C, Ser. No. 766,170, now Patent3,045,334, and RC. 2839-D, Ser. No. 765,017, now Patent 3,096,182.

The inventions disclosed in the aforementioned applications relate to aprocess wherein metallic surfaces and other catalytic surfaces ingeneral are contacted with an aqueous alkaline plating solutioncontaining nickel or cobalt salts, a borohydride and a complexing agentand to plates obtained using the process. The use of alkaline platingsolutions is necessary since the oxidation of borohydride ions by wateris very rapid in acid and neutral solutions. Due to the alkalinity ofthe solution, a complexing agent must be included in order to preventthe precipitation of nickel or cobalt hydroxide.

The present invention is directed to processes using simple aqueousplating solutions containing nickel and cobalt ions and to theproduction of nickel-boron and cobalt-boron alloy plates having theexcellent characteristics noted above. An essential feature of thepresent invention is the use of amine-boranes as a reducing agent and asa source of boron, preferably in acidic plating solutions, eliminatingthe necessity of including a sequestering or complexing agent for thenickel and cobalt ions being reduced upon contacting the catalyticsurface. Amine-boranes, however, function as excellent reducing agentsand as sources of boron over a wide pH range and may be included inhighly alkaline plating solutions. It is necessary, however, to employ asequestering or complexing agent in the event an alkaline platingsolution is selected as the plating medium in order to form nickel andcobalt complex ions, preventing the formation of the insolublehydroxides of nickel and cobalt.

It is an object of this'invention to provide a novel chemical platingprocess for the deposition of nickel and cobalt in the form of theirboron-containing alloys from an aqueous solution on the surface of anobject, which surface catalyzes the plating or deposition of the nickelor cobalt alloy from the solution.

It is another object of this invention to provide new aqueous chemicalplating solutions which are stable, easily formed and which may bereadily controlled to plate nickel-boron and cobalt-boron alloys on acatalytic surface at a fast plating rate.

It is still another object of this invention to provide new aqueouschemical plating solutions from which hard, adherent, corrosionandwear-resistant coatings of nickelboron and cobalt-boron alloys can bechemically deposited on catalytic surfaces.

3,338,726 Patented Aug. 29, 1967 ICC Other objects of the invention willbecome apparent from the following detailed description of theinvention.

Plating is accomplished by initially forming an aqueous plating solutionhaving a pH 3.5-14 which contains simple or complex nickel or cobaltions and an amine-borane. Nickel-boron and cobalt-boron alloys may thenbe chemically deposited in uniform layers from such plating solutions onarticles which have catalytic surfaces. There are preferredconcentrations of the components taking part in the plating process inaddition to temperature and pH ranges and other factors which lead tooptimum plating conditions. However, it is to be understood thatnickelbo ron and cobalt-boron alloys may be plated chemically fromsimple aqueous solutions by reducing nickel and cobalt ions on acatalytic surface where such reduction is fostered by an amine-borane.The reaction is carried out in an aqueous solution at a pH that does notrapidly decompose the amine-borane until it comes into contact with acatalytic surface.

The term catalytic surface as used in connection with my chemicalplating process refers to the surface of any article which contains,either in whole or in part, a material which promotes on its surface thereduction of nickel or cobalt ions. Such reduction is believed to bepreceded by the decomposition of the amine-borane with the formation ofatomic hydrogen at the catalytic surface.

Surfaces of glass and various plastics are, in general, noncatalytic.However, these surfaces can be sensitized to be catalytic by producing afilm of one of the catalytic materials on these surfaces. This can beaccomplished by a variety of techniques known to those skilled in theart. A preferred procedure involves dipping articles of glass or plasticin asolution of stannous chloride and then contacting the treatedsurface with a solution of palladium chloride. A monolayer of palladiumis thus produced. The article can then be chemically plpated withbickel-boron or cobalt-boron alloys by the process of this invention.

Those surfaces which are known to promote and catalyze such reductionare essentially the same surfaces disclosed in my copending applicationsfiled of even date and include nickel, cobalt, iron, steel, aluminum,zinc, pallabilities augmented by the addition of hydroxyl or otherhighly polar groups to the amine substituent in accordance withconventional practices.

It is known that amine-boranes are decomposed by oxidation in aqueoussolution to yield the amine, boric acid and hydrogen gas. In theinstance of dimethylamineborane, the following reaction takes place:

, (CH HN+H BO +3H The rate of this reaction, which is typical ofamineboranes,

depends on several factors including temperature and hydrogen ionconcentration. Increases of temperature and concentration of hydrogenion increases the decomposition of amine-boranes, but the rate ofdecomposition, even at a pH as low as 3.5, is still slow enough to findapplication in the instant process.

Generally, all amine-'boranes possess sufiicient stability to resistrapid decomposition in pH 3 solutions. The presence of a catalyticsurface accelerates the rate of decomposition. Tertiary amine-boranespossess good stability and may be efficiently employed in my process,using a plating solution with a relatively high temperature.

Boranes with EH attached to the nitrogen atom of a heterocycliccompound, such as pyridine and analogs thereof, generally behave and arereferred to herein as tertiary amine-boranes.

Secondary amine-boranes appear to possess sufficient stability to beused in acidic solutions having a pH 3 and yet decompose readily on acatalytic surface at an efficient rate. Some of the amine-boranes arenot as suitable as others but still decompose on catalytic surfaces atslow rates and hence are operative.

The nomenclature of many of the amine-borane compounds, which may besuccessfullyemployed in my process, has not been fully appraised.However, it is a common characteristic of those compounds, wherein thehorane substituent (EH is attached to the nitrogen atom of an amine, todecompose and operate as an efiective reducing agent under theconditions outlined herein.

The concentration of the amine-borane in aqueous solutions is importantto the rate of plating, but not determinative as to operativeness sincethe presence of even minute amounts of amine-boranes permits the platingof alloys. High concentrations of amine-boranes, including saturatedaqueous solutions of those very soluble amineboranes, likewise admitplating. As a practical matter, concentrations where the amine-borane ispresent within the range of 0.015 to about 0.2 g. mole/liter arepreferred.

Nickel and cobalt ions may be introduced in aqueous solutions by simplyadding an appropriate amount of a watersoluble salt such as the sulfate,chloride, acetate, for-mate, etc., salts of nickel and cobalt. Salts ofstrong oxidizing acids and those which include anions such as sulfide,cyanides and thiocyanates should not be used since they tend tointerfere with the reduction process. The lattermentioned antagonisticsalts, however, are not normally employed as sources of nickel andcobalt ions.

Additional ways of introducing nickel and cobalt ions will occur tothose skilled in the art. For instance, nickel oxide in the presence ofsmall amounts of hydrochloric or sulfuric acid is a common methodemployed to that end.

The concentration of nickel and cobalt ions in solution is not in anyway critical and may vary over a wide range. The rate of plating isslightly increased with increases in the concentration of nickel andcobalt ions. An initial concentration of from 0.02 to 0.5 g. mole/ literof salt is preferred.

The nickel or cobalt complexing or sequestering agents suitable for usein accordance with this invention include ammonia and organiccomplex-forming agents containing one or more of the followingfunctional groups: primary amino group (NHg), secondary amino group NH),tertiary amino group N), irnino group (:NH), carboxy group (COOH), andhydroxy group (OH). Preferred agents include ethylenediamine,diethylenetriamine, triethylenetetramine, ethylenediamintetraaceticacid, citric acid, tartaric acid, lactic acid and ammonia. Relatedpolya-mines and N-carboxymethyl derivates thereof may also be used.

In carrying out the plating process, the surface to be plated, normallyformed of a metallic catalytic material, may be prepared by mechanicalcleaning, degreasing and acid pickling, according to standard practicein electroplating processes. The cleaned surface is then immersed in asuitable volume of the aqueous plating solution. A1- most immediately,hydrogen bubbles can be observed forming on the catalytic surface of thearticle and escaping in a steady stream from the bath, while the surfaceof the article becomes slowly coated with a metallic plate. Plating iscontinued until the metal ions are depleted from solution, or until theevolution of hydrogen gas stops, indicating that all the amine-borane isconsumed in the plating process.

A method for the quantitative determination of amineboranes has beendevised. This comparatively simple method can be carried out todetermine the amount of amine-borane in plating solutions; the additionagents that are ordinarily in plating solutions do not interfere withthe analysis. This method is based on the knowledge that amine-boranesare easily oxidized by iodine in weak acidic solutions. By buffering asolution containing an amine-borane with sodium acetate and acetic acid,a rapid analysis may be carried out with the addition of star-chfollowed by titration with iodine (I solution. The end points in thetitration are sharp; the reaction proceeds rapidly and quantitatively asindicated in the following equation:

Quantitative determinations by the iodine titration method closelyapproximate those results obtained by the convention hydrogen evolutionmethod. The latter-referredto method, based on hydrolysis ofamine-boranes to boric acid and hydrogen, is often unsatisfactory foranalyzing plating solutions.

If there were no metal ions being reduced, substantially all of thehydrogen would be in molecular form (H as indicated in Equation 1 aboveand the pH would increase somewhat because of the free amine. As thenickel or cobalt ions are reduced, electron transfer occurs at thecatalytic surface with the formation of hydrogen ions and the pH islowered. In order to maintain the pH of the bath within the desiredrange, a buffering system can be advantageously included. Such a systemwill sustain a substantially constant plating rate and assist topreserve the stability of the bath.

Unlike electroplating processes which necessitate the use of platingsolutions that contain a very restricted variety of components, thepresent invention is relatively free from those limitations imposed byion migration and anode contamination and practically any bufferingsystem may be used.

Those buffering systems which contain acids and acid salts havingcyanide, thiocyanate and sulfide radicals are antagonistic to theplating process for the reasons noted above. However, buffering systemsnormally do not contain radicals antagonistic to the process disclosedherein and virtually any system may be used.

Both acidic and alkaline buffering systems are operative in generalincluding the common carboxylic acids such as acetic, propionic, etc.When an acidic pH is to be maintained, an acid with a pK 3 should beselected. The solution may be buffered by adding a weak acid andadjusting the pH with a base, or both the weak acid and its salt may beadded in the desired amounts. Another Way is to add the salt of a weakacid and a strong acid. This method is not preferred inasmuch as theacid anion and salt cation will be present in solution.

Many of the components included in the buffering systems are capable offorming complex ions with nickel and cobalt ions in the platingsolutions. However, the formation of complex ions is in no waydetrimental to the process. In fact, the formation of nickel or cobaltcomplex ions is necessary and beneficial in the event the platingsolution is alkaline.

The particular buffering system employed may require the addition ofsodium hydroxide or hydrochloric acid to adjust the pH within a certaindesired range. Such adjustments are well known to those in the field andone skilled in the art can readily determine the amounts of the variousreagents required to adjust the pH.

The rate of plating is an important consideration when devising acommercially feasible plating process. It is influenced by many factorsincluding (1) pH of the plating solution, (2) concentration of amineborane, (3) temperature of plating bath, (4) concentration of nickel orcobalt ions, (5) ratio of volume of bath cmfi/area plated cm. (6)presence of soluble fluoride salts and (7) presence of wetting agentand/ or agitation.

In general, the rate of plating increases as the pH value is increased.Plating may be done in solutions at a pH 3.5 to 14 although a pH l isoften impractical. An increase in the concentration of amineborane alsoincreases the rate of plating. At a constant pH, the rate isapproximately proportional to the amineborane concentration. As thetemperature increases, the rate of plating increases. As a practicalmatter, most plating processes will be carried out above 40 C. andpreferably at a temperature of at least 60 C. up to the boiling point ofwater.

It has been found that the addition of soluble fluoride salts, such assodium fluoride, increases the rate of plating. In addition to sodiumfluoride, other soluble fluoride salts may be used providing that theaction is inert with respect to the other ingredients in the platingsolution. Soluble fluoride salts may be used in the amount of a trace tosubstantially larger concentrations.

The above four 'factors have the most important influences on the rateof plating which may 'be readily adjusted according to the needs of theparticular process employed.

An increase in the concentration of nickel or cobalt ions only slightlyincreases the rate of plating. The larger the ratio of the volume ofplating bath (cm?) to the area of the surface being plated (cm. thehigher will be the rate of plating since nickel or cobalt ions and theamine-borane reducing agent are depleted slowly. The above ratiopreferably has a value of 1 to 10.

The chemical plating of nickel-boron or cobalt-boron by chemicalreduction with amine boranes is accompanied by the evolution of hydrogengas according to Equation I noted above.

The presence of a gas bubble on the surface interferes with the contactbetween the plating solution and the particular spot where the bubble isbeing formed. This obviously leads to lower rates of plating andsometimes also to the formation of a pit in the plate. Difiiculties ofthis nature, which are also frequently encountered in the conventionalelectroplating, can be eliminated by reducing the contact time betweenthe gas bubble and the surface by proper stirring of the bath and/or byadding wetting agents to decrease the surface tension of the platingsolution, preferentially below 50 dynes per cm. The use of wettingagents is recommended when plating is done at lower temperatures.Wetting agents such as sodium lauryl sulfate and the like are suitable.

The plating operation may be maintained by continuously orintermittently adding amine-borane, a salt source of 'nickel or cobaltions, and the other ingredients consumed. When a buffering system isemployed, it can be maintained by the addition of a base. Generally, themolar ratio of the ingredients used in a buffering system and as acomplexing or sequestering agent to the salt source of the nickel orcobalt ions should be between 4.0 and 0.2.

The initiation of the plating process can be speeded up, particularlywhen working at temperatures below about 70 C., by contacting thesurface of the material to be plated with a more electro-negative metalsuch as 'aluminum, while in contact with the plating solution.

Since nickel and cobalt and their alloys with boron are good catalystsfor the reduction of the nickel or cobalt 3 ions to metallic nickel orcobalt in the presence of amineboranes, once the initial deposit ofthese metals is obtained upon a surface, the plating will continue aslong as the solution remains workable.

The plating solution is preferably contained in glass or plastic vesselssince their surfaces are generally noncatalytic and will not initiatethe deposition of nickel or cobaltboron alloys when contacted with theplating solutions.

The efliciency of the bath is often impaired to some extent bycontamination with impurities. Those impurities which act as minutecatalytic surfaces should be rigorously excluded. In the eventimpurities of this nature exist and begin to increase in size withdeposits of the plating alloy, the solution should be filtered orpurified by activated charcoal.

Frequently, the addition of small amounts of some organo sulfur compoundor lead salts (1-50 parts/million) will render inert those impuritiesthat are present in the plating bath. Such sulfur compounds as thioureaand xanthates are well-known for this purpose as are various lead saltsand may be used when necessar'r Plates of nickelor cobalt-boron alloysare essentially the same plates obtained by the process disclosed in myaforementioned copending applications. While the plates are difficult toanalyze, it has been recently determined, through X-ray diffraction andX-ray microscopy techniques, that the boron is irnbedded in an amorphousmatrix of the metal placed in both nickelor cobalt-boron platingprocesses. The matrix metal is essentially amorphous to X-rays (CuK,radiation, e.g.) showing only about 5l0% crystalline nickel or cobalt.

All alloy plates that are prepared in accordance with the presentinvention contain about 92'99% of nickel or cobalt and about l8% boron.Approximately 510% of the metal is present as crystalline nickel orcobalt; the remainder of the metal is structurally unorganized andnoncrystalline. The boron and crystalline metal are uniformly dispersedand distributed throughout the matrix.

After heat treatment for one hour at 600 C., the X-ray diffractionpatterns of nickel-boron plates show the presence of crystalline Ni Band additional crystalline nickel, indicating that boron and nickel havechemically reacted and that the small amount (5-10%) of crystallinenickel originally present has grown.

It has been further found that the amount of crystalline nickel presentin the amorphous matrix is as high as about 10% of the total nickelcontent present and possibly higher. The amount of crystalline cobaltpresent in the amorphous matrix of cobalt is frequently lower, sometimescomprising less than 5%.

The addition to the bath of buffers, complexing agents and the like willgenerally reduce the amount of boron deposited in the plate, especiallyin the instance of cobaltboron plates. Under varying conditions incobaltboron plating baths, the amount of boron in the plate may be aslow as about 1%. All of the plates obtained through the practice of theherein-disclosed invention, however, will contain about 18% by weight ofboron. Nickel-boron plates containing about 37% boron are produced bypreferred methods and have shown excellent qualities.

Plate containing both nickel and cobalt in addition to boron may beobtained using a plating solution containing a mixture of nickel andcobalt salts. When equivalent amounts of nickel and cobalt salts areused in the same plating bath, cobalt ions are preferentially reduced,and nickel-boron alloy plates so produced contain a higher percentage ofcobalt than nickel. Although nickel is preferred for economic reasons,cobalt and nickel are considered to closely approximate one another forthe purposes of the present invention.

In addition to the excellent qualities noted above, plates produced asdisclosed herein are useful as ornamental designs, since a non-catalyticsurface may be selectively activated by the use of stannous chloride andpalladium chloride as described above. Similarly, these metal plates maybe deposited in predetermined'patterns that serve as electricalconductors. Circuit patterns may thus be selectively plated on theactivated areas of an inexpensive sheet of material that is normallynoncatalytic.

Examples illustrating various plating baths and conditions under whichthe process may be carried out follow.

Example 1 Using nickel chloride as a source of nickel ions anddimethylamine-borane, steel samples were plated at varying temperatures.

G. mole/liter NiCl 0.1 (CH HNBH 0.06

The ratio of the volume of plating bath to area of surface being platedwas 1.5. The rate of plating was determined from weight increase.

Temperature, 0. Rate of Plating,

rug/em in 15 min.

Percent of 100 C.

Using cobalt chloride instead of nickel chloride and isopropylamine-borane (C3H7)H2NBH3 in equimolar amounts, the rate of platingcobalt-boron alloy on steel likewise markedly decreases as thetemperature is lowered.

In addition to dimethylamine-borane and isopropyl amine-borane at theabove concentration of 0.06 g. mole/ liter, ethylarnine-borane andtertiary propylamine-borane are used at the same concentration inplating baths, together with 0.1 g. mole/liter of NiC1 Decreasing thetemperature also decreases the plating rate.

Example 2 Excellent results are obtained plating copper, steel or othercatalytic surfaces using aqueous plating solutions containing NiCl g.mole/liter" 0.1-0.2 (CH HNBH do 0.05-0.08 CH C0OH+CH COONa do 0.15-0.30pH 5.0-5.5 Temp. C 70-75 Volume (cm. )/area (cm?) 5-10 Rate of platingmil/hr. 0.8-1.0

1 1 mil/hr. approximates 22 mg./.cm. per hr.

This preferred plating solution gives the same excellent results wheneither succinic acid, lactic or tartaric acid is used instead of aceticacid in the same amounts and the pH is adjusted to the above range withNaOH.

Example 3 Using a plating bath (50 cm?) containing 0.1 g. mole/ liter ofNiCl and 0.075 g. mole/liter of (CH HNBH clean steel samples (33 cm?)were plated in this solution at 60 C. for 15 minutes. The rate ofplating is 1.2 mg./ cm. The same solution containing 0.1% by weight ofsodium lauryl sulfate as a Wetting agent plates at a rate of 1.9 mg./cm.under the same conditions.

Example 4 A plating solution of the following composition was used toplate copper and steel surfaces:

G. mole/liter NiCl 0.1 (CH HNBH 0.06 Mixture of tartaric acid and cone.ammonium hydroxide to give tartrate conc. of 0.2 g. mole/liter and pH of8. Temp. 50 C. Volume (cm 1 35 Area (CD12) Rate of plating 1.8 mg./cm.in 30 min.

8 Example 5 NiCl g. rnOle/lit1' 0.1 .dO Ethylenediamine dO 0.4 pH 11.0Temp. C 70 Volume (cm Area (cm Rate of plating on copper or steel isabout 0.3 rug/cm. in 15 min. Cobalt chloride in the same amount platesin the same alkaline bath.

Example 6 C080 g. mole/liter 0.05 (CH HNBH do 0.075 CH COOH+CH COONa do0.25 pH 5.2 Temp. C 75 Volume (cm Area (cm Rate of plating on coppersurface was 0.8 mg./crn. in 30 minutes.

Example 7 NiCl g. mole/liter 0.1 Na;.; citrate do 0.25 Pyridine-borane(C H NBH do 0.25 pH 6.5 Temp. C 98-99 Volume (cm Area (cm Rate ofplating on copper is 0.3 mg./crn in 30 min. The rate of plating on steelis comparable with that of copper. Other catalytic surfaces can also beplated using a plating solution containing the above components in theamounts set forth and they may be plated with either cobalt-boron ornickel-boron alloys.

Temperature: 98-99 C. Material of samples plated: copper Volume ofplating solution (cm?) Area of the sample (cm?) Substituting equalamounts of methylethylamine-borane and diethylamine-borane fordimethylamine-borane, plating baths are prepared having the sameconcentrations of NiCl and temperatures of 98-99 C. Increasing concentrations of these amineboranes also increases the rate of plating oncopper surfaces. The ratio of plating solution volume/area is about 5.

Example 9 Initial Composition of Plating Solutions in g. mole/liter Rateof Plating,

mg./cm. in 15 min.

NiCl; (CHWHNBH NaF 0.1 M 0.060 M 2 2 0.1M 0000M 001 M 27 0.1 M 0.060 M 0025 M 2 9 0.1M 0060M 005 M 34 Other conditions are the same as inExample 8. Other alkali metal fluoride salts when used in the sameconcentrations as N'aF, likewise increase the rate of plating, as doesNil-" NH F and the like.

Example 10 Initial Composition of'Plating Solutions in g. mole/literRate of Plating,

pH mg./cm. in 15 min.

NiCl, (CHmHNBH;

0.1 M 0.030 M 1.1 0.1 M 0.030 M 4.0 1.4 0.1 M 0.030 M 4.6 1.6 0.1 M0.030 M 5.3 1.9 0.1 M .0.030 M 5.6 2.1 0.1 M 0.015 M 5.3 1.0 0.1 M 0.030M 5.3 1.9 0.1 M 0.060 M 5.3 3.8 0.1 M 0.090 M 5.3 5.2 0.2 M 0.060 M 5.33.8 0.1 M 0.060 M 5.3 3.8 .05 M- 0.060 M .3 3 .0 0.025 M 0.060 M 5.3 2.0

1 Without buffer.

The plating solutions were made 0.35 molar in acetic acid, and the pHwas adjusted to the above values with sodium hydroxide. Other conditionsare the same as in Example 8. Using CoSO in amounts which yield cobaltions in concentrations equal to nickel ion concentrations above, anincrease in the pH of the plating bath likewise increases the rate ofplating.

Example 11 Clean copper surfaces having different areas were plated inseparate 50 ml. baths for 1 hr. The composition of the bath was NiCl g.mole/liter 0.1 (CH HNBH -do 0.17 CH COOH+CH COONa do.. 0.27 Sodiumlauryl sulfate percent 1 0.1 pH 5.5 Temperature C 60 1 By weight of thebath.

When the ratio has a value of about 10, the rate of plating is seen tobe relatively efiicient as compared to higher ratio values.

Ammonia borane H NBH prepared by reacting lithium borohydride withammonium chloride in diethyl ether, is substituted fordimcthylamine-borane in the same amount in this plating bath. Increasingthe ratio of volume (0111. area. (cm?) likewise increases the rate ofplating.

Certain theories relating to the disclosed process have been advanced,but it is to be understood that I do not intend to be limited to suchtheories. They have been advanced to assist those skilled in the art.Modifications and adaptations of the herein disclosed invention willoccur to those skilled in the art, but it is to be further understoodthat I do not wish to be limited except as indicated in the appendedclaims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A chemical plating bath comprising an aqueous solution having a pH ofat least 3.5, said solution containing 10 an amine-borane and a cationselected from the group consisting of nickel and cobalt ions.

2. A chemical plating bath comprising an aqueous acidic solution havinga pH within the range of 3.5 to about 7, said solution containing anamine-borane and a cation selected from the group consisting of nickeland cobalt ions.

3. A chemical plating bath comprising a buffered aqueous acidic solutionhaving a pH Within the range of 3.5 to about 7, said solution containingan amine-borane and a cation selected from the group consisting ofnickel and cobalt ions.

4. A chemical plating solution comprising an aqueous alkaline solution,said solution containing an amineborane, a cation selected from thegroup consisting of nickel and cobalt ions and a metal sequesteringagent, said cation being in the form of a complex ion.

5. The process of chemically plating a catalytic surface with an alloyselected from the group consisting of nickel-boronand cobalt-boronalloys comprising contacting said surface with an aqueous solutionhaving a pH of at least 3.5, said solution containing an amine-boraneand a cation selected from the group consisting of nickel and cobaltions.

6. The process of chemically plating a catalytic surface with an alloyselected from the group consisting of nickelboron and cobalt-boronalloys comprising contacting said surface with an aqueous solutionhaving a pH of at least 3.5, said solution containing an amine-borane, acation selected from the group consisting of nickel and cobalt ions anda soluble fluoride salt.

7. The process of chemically plating a catalytic surface with an alloyselected from the group consisting of nickelboron and-cobalt-boronalloys comprising contacting said surface with an aqueous solutionhaving a pH of at least 3.5 and a temperature within the range of toabout 100 C., said solution containing an amine-borane and a cationselected from the group consisting of nickel and cobalt ions.

8. The process of chemically plating a catalytic surface with an alloyselected from the group consisting of nickelboron and cobalt-boronalloys comprising contacting said surface with a plating solution ofclaim 1.

9. The process of chemically plating a catalytic surface with an alloyselected from the group consisting of nickelboron and cobalt-boronalloys comprising contacting said surface with a plating solution ofclaim 3.

10. An aqueous chemical plating solution containing as essentialcomponents (1) a compound selected from the group consisting ofsecondary and tertiary amine boranes, and (2) a compound selected fromthe group consisting of soluble salts of nickel and cobalt, theproportions of each component being such that the concentration ofborane radical is between 0.021 to 0.276 wt. percent, and theconcentration of metal ion is between 0.12 to 2.94

' wt. percent.

11. A method of platiing metal-boron alloys on metal objects whichcomprises the step of contacting the object to be plated with an aqueousplating solution containing as essential components (1) a compoundselected from the group consisting of secondary and tertiary amineboranes, and (2) a compound selected from the group consisting ofsoluble salts of nickel and cobalt, the proportions of each componentbeing such that the concentration of borane radical is between 0.021 to0.276 wt. percent and the concentration of metal ion is between about0.12 to 2.94 wt. percent.

12. A method according to claim 11 in which the amine borane isdimethylamine borane.

13. A method according to claim 11 in which the pH of the platingsolution is maintained between 3.5 and about 7.

14. A method according to claim 13 in which the pH is maintained bybuffering the solution with a weak nonoxidizing acid.

15. A method according to claim 11 in which the borane radicalconcentration is maintained by the periodic addition of amine borane.

16. A method according to claim 11 in which the metal ion concentrationis maintained by the periodic addition of a soluble metal salt.

17. A bath for plating by chemical deposition consisting essentially ofan aqueous solution containing a metal salt selected from the group ofwater soluble salts of nickel and cobalt, and isopropylamine borane in amolar ratio between about 2 to 1 and 3.3 to 1 wherein the concentrationof said isopropylamine borane in said solution is about 1 to 2 grams perliter.

18. A bath for plating by chemical deposition as claimed by claim 17wherein the metal salt and the isopropylamine borane are present in saidsolution in the molar ratio of about 3 to 1.

19. A bath for plating by chemical deposition as claimed by claim 17wherein the metal salt is nickel chloride.

20. A bath for plating by chemical deposition as claimed by claim 18wherein the metal salt is nickel chloride.

l 2 References Cited UNITED STATES PATENTS 2,694,019 11/1954 Gutzeit117-130 2,721,814 10/1955 Jendrzynski et al 106-1 2,726,170 12/ 1955Warf 117-65 2,942,990 6/ 1960 Sullivan 117-130 2,990,296 6/1961 Hoke117-130 OTHER REFERENCES Hurd: Chemistry of the I-I ydrides, 1952, Pub.by John Wiley & Sons Inc., New York, p. 85 relied upon.

Stone: Chemistry of the Boron Hydrides, 1955, p. 193.

15 MORRIS LIEBMAN, Primary Examiner.

JOSEPH B. SPENCER, RICHARD D. NEVIUS,

Examiners.

1. A CHEMICAL PLATING BATH COMPRISING AN AQUEOUS SOLUTION HAVING A PH OFAT LEAST 3.5, SAID SOLUTION CONTAINING AN AMINE-BORANE AND A CATIONSELECTED FROM THE GROUP CONSISTING OF NICKEL AND COBALT IONS.